It has been recognized for several years that power ultrasound can effectively inactivate algae cells at a laboratory scale. However, although ultrasonic inactivation shows great potential, there are few reports of its use when applied on a large scale. In this study, we have investigated the uses of two types of ultrasonic equipment at a small and medium laboratory scale for the control of algae blooms which are commercially available in similar configurations for industrial scale operation.

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... e following equipment was tested using cultured algae suspension: (a) Dual Frequency Reactor (DFR) operating on 1 L in batch mode and 3.5 L in recirculating mode with two resonating plates at different frequencies of 16 and 20 kHz (Advanced Sonic Processing Systems, USA); (b) Sonolator operating in a flow mode treating 5 L using hydrodynamic cavitation (Sonic Corporation, Stanford, CA, USA). The most effective inactivation was obtained using the DFR in batch mode at 60% power setting for 10 min which resulted in a reduction of 60% of the original concentration (measured using optical density OD). In a recirculating loop mode, the treatment of 3.5 L algae suspension with a DFR for 15 min resulted in a reduction of 46% (OD). Ultrasonic treatment of 5 L suspension in a recirculating loop using the Sonolator over 5 h resulted in a reduction of 30% (OD). This study is the first to explore the use of two commercially available ultrasonic systems (DFR and Sonolator) both capable of direct scale-up to industrial levels for the control of algae. It demonstrates that sonication in a recirculating process has the potential to be effective in the treatment of algal cells on a large scale.